Low hysteresis sealant composition for self-sealing tire

ABSTRACT

This invention is based upon the unexpected finding that the reaction product of polyisobutylene and a silane can be incorporated into tire sealant formulations to greatly reduce the level of hysteresis exhibited by such sealant formulations which decreases the rolling resistance of the tire to improve fuel economy. This is made possible by the further unexpected fining that silanes will react with polyisobutylene by a reaction which is initiated with a peroxide. This invention more specifically discloses a sealant composition which is particularly useful in manufacturing self-sealing tires and which is comprised of (a) the reaction product of polyisobutylene and a silane; and (b) a reinforcing filler. The sealant compositions also contain a peroxide to facilitate partial degradation of the polyisobutylene rubber during the curing of the tire.

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 63/286,725, filed on Dec. 7, 2021. The teachings of U.S.Provisional Patent Application Ser. No. 63/286,725 are incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to a pneumatic tire of the tubeless type withpuncture sealing properties, the puncture sealing composition used insuch tires which exhibits a low level of hysteresis, and the method formanufacturing such tires.

BACKGROUND OF THE INVENTION

Historically, puncture sealing tires have been designed in such a way soas to retard or prevent the loss of air and consequential deflation ofthe tire after being punctured with a sharp object, such as a nail.Pneumatic tires with puncture sealing capabilities have been describedin the literature since at least the first part of the twentieth century(see U.S. Pat. Nos. 1,419,470, 1,601,013, and 1,977,281). Such earlyself-sealing tires were of a relatively simple design that generallyincluded an unvulcanized layer of rubber which would theoretically flowinto the puncture and seal it so as to prevent air loss. However, inactual practice such self-sealing tires were not very effective andconsequently were of limited value.

Over the years better puncture sealing tires have been developed whichallow for the tire to provide longer service after being punctured. Inmany cases, this provides for the continued use of the tire until it canbe driven to a more convenient location for it to be repaired orreplaced. For instance, it would be highly desirable if the vehicle onwhich the tire is installed could be driven to a garage or a tireservice center for repair rather than being required to change the tireon a busy road, under inclement weather conditions, or in a less thandesirable neighborhood. In any case, more and more sophisticated tireconstructions, sealant compositions and methods for manufacturingself-sealing tires have been developed. In most of these designs asealant material is encased or encapsulated in between layers of thetire. For example, U.S. Pat. No. 2,877,819 discloses a unitary tubelesspneumatic tire, comprising a hollow casing of fabric reinforcedvulcanized, rubber-like elastic material and including a circumferentialtread portion of substantial width and opposite sidewalls extendingradially inwardly therefrom, and an annular puncture-sealing body ofsubstantial width on the inner periphery of said casing in laterallycentered relation with respect to said tread portion and sidewalls, saidbody including radially inner and outer walls of rubber-like materialintegrally connected at laterally spaced peripheral side portions of thebody and said outer wall being integrally connected at laterally spacedperipheral side portions of the body and said outer wall beingintegrally cured to the elastic material of said fabric reinforcedcasing, said body having web portions integrally connecting between saidinner and outer walls thereof defining a plurality of separate callscompletely around the body, and said cells containing puncture-sealingmaterial, said web portions being uniformly relatively thin, wherebysaid cellular body between said inner and outer walls thereof ispredominantly puncture sealing material so that a puncturing objectpenetrating the tread portion of said casing and said body atsubstantially any point must pass through sufficient said puncturesealing material to seal against escape of inflation air through thepuncture made by the puncturing object.

U.S. Pat. No. 3,048,509 discloses a laminated puncture sealing strip forpneumatic tires comprising a plurality of superposed sealing sheets thatare not more than about one-tenth inch or less than about one-twentiethinch in thickness and that are composed of a soft sticky unvulcanizedsynthetic rubber sealing composition comprising a copolymer of1,3-butadiene and styrene which contains at least 50% by weight of thediene combined with 35 to 115 parts by weight of softening andtackifying agents per 100 parts of the copolymer and with from 35 to 65parts by weight of a pigment per 100 parts of the copolymer, saidsoftening and tackifying agents and pigments being so proportioned thatsaid sealing composition has a plasticity of from 20 to 35 as measuredon a Neodoptifa-Hoekstra plastometer, and means for restricting flow ofthe sealing composition and for protecting the same againstdeterioration comprising separating and covering sheets alternating withthe sealing sheets, said separating and covering sheets being thinnerthan said sealing sheets and being composed mainly of a vulcanizedrubber compound the principal rubbery component of which is selectedfrom the group consisting of a polymer of chloroprene andstyrene-butadiene rubbers than contain at least 50% by weight of thediene, said rubber compound being substantially free from sulfur andmigratory curing agents. U.S. Pat. No. 4,089,360 discloses a pneumatictire having a laminate as an abrasion gum strip or an innerliner whereinsaid laminate is comprised of at least two groups of layers with eachgroup having at least one layer and each layer of said laminatecomprising a rubber compound having an unsaturated, amorphous polymerselected from the group consisting of natural rubber and syntheticrubber and each layer having sulfur and sulfur cure accelerators so thatsaid layers will vulcanize when exposed to a subsequent vulcanizationtreatment, said laminate manufactured by the steps comprising providingat least one layer of a first group with a component selected from thegroup consisting of paradichlorobenzene and the thioetherpolythiols;providing at least one layer of a second group with components selectedfrom the group consisting of 2,6-di-t-butyl-p-cresol; phenylbeta-naphthylamine; 4,4′ thiobis (6-t-butyl-m-cresol);N-(1,3-dimethylbutyl) N′ phenyl-p-phenylene diamine;syn-di-betanaphthyl-p-phenylene diamine; and aromatic oils; saidcomponents yielding different degrees of cross-linkage in said layerswhen said layers are subjected to irradiation; assembling at least oneof said layers from each said group into contiguous relationship to forma laminate; subjecting said laminate to irradiation so that at least twoof said layers are cross-linked to a different degree; assembling saidlaminate into said tire and vulcanizing said tire.

U.S. Pat. No. 4,140,167 discloses a pneumatic tire comprising as one ofits rubber elements a laminate comprising at least five layers of rubbercompounds produced by providing at least two outer layers with adesensitizing agent which retards cross-linkage when subjected toirradiation, providing two inner layers of said laminate with asensitizing agent which promotes cross-linkage when subject toirradiation, providing a middle layer located between said sensitizedlayers with a material which degrades when exposed to irradiation,assembling said laminate with said middle layer located between the twosensitized layers and the one of said desensitized layers locatedoutside of each of said sensitized layers, subjecting said laminate toirradiation so that said layers are differentially cross-linked withsaid sensitized layers being cross-linked to a greater degree than saiddesensitized layers and said middle layer being degraded to yield a softproduct, assembling said laminate into said tire and vulcanizing saidtire. The degraded polymeric material utilized in such tires can bepolyisobutylene, copolymers containing polyisobutylene, or polyethyleneoxide, and the cross-linked polymeric material can be natural rubber,copolymers of butadiene and styrene and halogenated butyl rubber.

U.S. Pat. No. 4,228,839 discloses a self-sealing pneumatic tirecomprising an annular road-engaging tread surface, two sidewalls eachconnecting a side of said tread surface to an annular bead, reinforcingbody plies extending from one bead to the other through the sidewallsand tread and a puncture-sealant layer located in the crown area of saidtire radially inward of said reinforcing body plies, saidpuncture-sealant layer comprising a blend of a first polymeric materialthat degrades on exposure to irradiation and a second polymeric materialthat crosslinks on exposure to irradiation, vulcanization temperaturesor both to form an elastic matrix for said first polymeric material,said tire manufactured by the steps comprising providing a layercomprised of blended rubber compound with said blend of said first andsecond polymeric materials, assembling said layer into an unvulcanizedtire as its innermost layer in the crown area, vulcanizing said tire,and subsequently irradiating said tire to degrade said first polymericmaterial whereby said first polymeric material forms a tacky material insaid second crosslinked polymeric material which acts as an elasticmatrix for said first polymeric material, whereby said layer with saidpolymeric material combination has puncture sealing properties. In thesetires, the first polymeric material can be polyisobutylene or acopolymer of polyisobutylene and the second polymeric material can be ahalogenated butyl rubber, an ethylene propylene terpolymer,polybutadiene rubber, a copolymer of styrene and butadiene, a blockcopolymer, a butadiene acrylonitrile copolymer, natural rubber,polyisoprene, or neoprene.

U.S. Pat. No. 4,426,468 describes a self-sealing composition for a tirebased on crosslinked butyl rubber having a very high molecular weight.U.S. Pat. No. 4,426,468 more specifically describes a butyl rubber basedsealant composition, the butyl rubber constituent of which is presentonly in the form of a copolymer having a viscosity average molecularweight in excess of 100,000, comprising the reaction product of saidbutyl rubber, a curing system including a cross-linking agent selectedfrom the group consisting of at least 2 parts by weight of a quinoidcross-linking agent per hundred parts butyl rubber and at least 5 partsby weight of a phenolic cross-linking agent per hundred parts butylrubber, and at least one tackifier compatible with butyl rubber, and afiller material, the composition being compounded such that it has atensile strength of at least 30 psi, an elongation of at least 600% anda cross-link density such that its swell ratio in toluene is between 12and 40. However, butyl rubbers have the drawback of exhibiting a highlevel of hysteresis over a broad temperature range which increased therolling resistance of tires and is detrimental of fuel economy.

As an alternative to butyl rubbers self-sealing compositions for tirescan also be made using unsaturated diene elastomers, including naturalrubber. Such compositions are described in U.S. Pat. Nos. 4,913,209,5,085,942, and 5,295,525. These compositions are characterized by thecombined presence of a high content of hydrocarbon resin as tackifier,always greater than 100 parts by weight per hundred parts. In addition,a large amount of liquid elastomer gives a high fluidity to thecomposition which is a source of other drawbacks, in particular a riskof the self-sealing composition flowing during use at relatively hightemperature (typically above 60° C.) frequently encountered during theuse of the tires in certain geographical regions.

U.S. Pat. No. 6,837,287 describes a method of manufacturing a pneumaticrubber tire having an outer circumferential tread, a supporting carcasstherefore, and an inner liner disposed inwardly from said supportingcarcass, containing a puncture sealant layer positioned between saidinner liner and said carcass, the steps of which comprise, based uponparts by weight per 100 parts by weight uncured butyl rubber (phr): (A)providing a butyl rubber-based rubber composition comprised of: (1) 100phr of uncured star branched butyl rubber, (2) about 1 to about 35 phrof a particulate precured rubber, selected from resin-cured butyl rubberand/or sulfur-cured diene-based rubber, homogeneously dispersed in saiduncured butyl rubber, and (3) about 1 to about 16 phr of organoperoxide;(B) assembling said butyl rubber based rubber composition as a layerinto an unvulcanized rubber tire between said carcass and saidinnerliner during the tire building process; and (C) shaping and curingsaid rubber tire at a temperature in a range of about 130° C. to about170° C. for a sufficient period time to partially depolymerize saiduncured butyl rubber in said butyl rubber-based rubber compositionlayer, wherein said particulate precured rubber substantially remains inits precured condition as a particulate dispersion within said partiallydepolymerized butyl rubber.

U.S. Pat. No. 8,221,849 discloses a method of producing a self-sealingpneumatic tire comprising the steps of: injecting a viscous sealantmaterial onto an internal surface of a vulcanization molded pneumatictire; rotating the pneumatic tire around a tire axis while forming thesealant material into a sealant layer diffused in a sheet form bycentrifugal force, injecting a cover material comprising an unhardenedrubber-based material or a resin-based material onto the internalsurface of the sealant layer; rotating the pneumatic tire around thetire axis while forming the cover material into a cover sheet layerdiffused in a sheet form by centrifugal force; and hardening the coversheet layer by irradiating with an electron beam, infrared rays,ultraviolet rays, or ultrasonic waves.

U.S. Pat. No. 8,360,122 describes a tire sealant material compositioncomprising at least one non-halogenated butyl rubber, and2,2′-dibenzamido-diphenyldisulfide, the sealant material compositionhaving a viscosity that permits the sealant material composition to beincorporated into a tire during a tire building process and to degradeto a lower viscosity that permits the resulting degraded sealantmaterial composition to flow into and seal a puncture in a tire.

U.S. Pat. No. 9,427,918 discloses a color sealant composition for atire, comprising: 100 parts by weight of a raw rubber, 10 to 60 parts byweight of surface modified silica prepared by placing silica at 300° C.to 500° C. for 30 minutes to 3 hours, 0.05 to 5 parts by weight ofpigment, 40 to 100 parts by weight of polybutene having a number averagemolecular weight of 1,000 to 1,500, 60 to 300 parts by weight ofpolybutene having a number average molecular weight of 2,000 to 3,000,and 5 to 15 parts by weight of peroxide. The raw rubber in this tiresealant composition can be natural rubber, butyl rubber, or a blend ofnatural rubber and butyl rubber.

U.S. Pat. No. 9,677,025 describes an inflatable article comprising apuncture-resistant layer, said layer comprising an elastomer compositionhaving a self-sealing property, wherein the composition comprises: ablend of at least two solid elastomers, a polybutadiene or butadienecopolymer elastomer, referred to as “elastomer A”, and a natural rubberor synthetic polyisoprene elastomer, referred to as “elastomer B”, theelastomer A: elastomer B ratio by weight being within a range from 10:90to 90:10; between 30 phr and 90 phr of a hydrocarbon resin; and from 0to less than 30 phr of filler.

U.S. Pat. No. 9,802,446 discloses a pneumatic vehicle tire comprising atread, an inner layer, and a tire sealant disposed upon the inner layerand opposite the tread; wherein the tire sealant comprises expandedsolids comprising expandable graphene structures and microspheres;wherein the expanded solids are incorporated into the tire sealant in anamount of from 1 weight percent to 20 weight percent and, wherein thetire sealant provides sealing by flowing into a defect site penetratingthe tread and the inner layer.

U.S. Pat. No. 10,730,255 describes a method of applying a rubber-basedself-sealing composition on an inner surface of a tire casing,comprising the steps of: introducing a non-crosslinked self-sealingcomposition into an inlet of an extrusion device; adjusting speed andtemperature conditions of the extrusion device so that, at anapplication nozzle forming an outlet die of said extrusion device, theself-sealing composition is crosslinked, and bringing the applicationnozzle close to the inner surface of said casing previously set inrelative motion with respect to the application nozzle, and depositingan extruded and crosslinked bead having a given width and profiledirectly on said internal surface of the casing; wherein the extrusiondevice includes an assembly comprising a screw rotated in a barrel, theextrusion device further including a duct positioning downstream of theassembly that opens into the application nozzle; wherein the extrusiondevice includes a plurality of zones, and the method further includesincreasing the temperature of the composition in a first zone to a setpoint temperature between 140° C. and 220° C. during a first period oftime, maintaining the temperature at the set point temperature in asecond zone for a second period of time, and increasing the temperaturein a third zone for a third period of time, wherein the third period oftime is shorter relative to the second period of time; wherein the thirdzone includes the duct and the application nozzle.

Many additional methods, sealants and tire constructions have beensuggested for puncture sealant pneumatic tires. However, all of theseideas have had certain drawbacks. For example, the use of fluid puncturesealant coatings which seal by flowing into the puncture hole arefrequently unsuccessful primarily because sealant coatings may flowexcessively and thus tend to cause the tire to become out of balance. Inother cases the sealant coating is not operable or effective over a widetemperature range extending from hot summer to cold winter conditions.Central cores of cellular material which will physically maintain theshape of the tire when punctured can place a restriction on the maximumspeed of a vehicle on which they are used because of potential breakdownor destruction of the cells caused by the effects of heat anddistortion. More complicated structures wherein the sealant material isencased in a vulcanized material are usually expensive to manufactureand can also create balance and suspension problems due to theadditional weight required in the tire.

Puncture sealing tires can be built wherein a layer of degraded rubberwhich is tacky or gummy (of low viscosity) is assembled into theunvulcanized tire. This method of construction is usually onlyreasonably possible when the degraded layer of rubber is laminated withanother rubber layer which is not degraded which permits its handlingduring the tire building procedure. This is because the tacky, stickynature and lack of strength in degraded rubber make it very difficult tohandle alone without additional support and a barrier to keep it fromsticking to a tire building machine or curing apparatus. By laminatingthe degraded rubber layer between two or more rubber layers which arenot degraded it is capable of retaining its structural integrity duringthe tire building and vulcanization process wherein high pressures areapplied to the tire which would displace the degraded rubber layer fromits desired location if not laminated. Such a lamination procedure addsgreatly to the cost of building a tire. Thus, such lamination procedureshave not been widely accepted on a commercial basis for buildingpuncture sealing pneumatic tires.

The most common commercial approach used in manufacturing self-sealingtires is to build a layer of degradable material which can be easilyhandled into the tire. This layer of degradable material is sandwichedbetween other layers of the tire. In many cases it will be positionedbetween two layers of innerliner or between the innerliner and thesupporting carcass of the tire. In any case, this degradable materialbreaks down at the elevated temperatures which are employed during thevulcanization of the tire into a low viscosity, tacky material. Thisapproach greatly facilitates the tire building procedure by eliminatingthe need to handle such a sticky material when the tire is being built.

Unfortunately, the sealant compositions utilized in making self-sealingtires typically exhibit high levels of hysteresis. In fact, conventionalsealant compositions are typically the most hysteretic material normallyused in manufacturing tires. Accordingly, their use in tires causes highlevels of heat build-up as the tire rolls as the vehicle on which theyare installed is drive during ordinary operation. This consequentlyresults in reduced fuel efficiency. There is consequently a long feltand continuing desire a sealant material that exhibits reducedhysteresis and which provides effective puncture sealingcharacteristics. It is, of course, also important for such a sealantmaterial to be capable of being easily build into high quality tiresusing conventional equipment using simple, low cost methods formanufacturing such tires on a commercial basis.

SUMMARY OF THE INVENTION

This invention is based upon the unexpected finding that the reactionproduct of polyisobutylene and a silane can be incorporated into sealantformulations to greatly reduce the hysteresis exhibited by such sealantformulations. This is made possible by the further unexpected findingthat silanes having no unsaturation will react with polyisobutylene byinitiating the reaction with a peroxide. The ability of this reaction totake place is particularly surprising in cases where a silane having nounsaturation is reacted with the polyisobutylene which, of course, isalso fully saturated. In any case, the incorporation of the reactionproduct of a silane and polyisobutylene into tire sealant formulationssignificantly reduces the level of hysteresis exhibited by the sealantand consequently decreases the rolling resistance of the tire to improvefuel economy. In other words, the subject invention provides a simpleand inexpensive method for manufacturing self-sealing pneumatic rubbertires of the tubeless type which generate less heat during operation andwhich consequently provide better fuel economy than conventionalself-sealing tires.

This invention more specifically discloses a sealant composition whichis particularly useful in manufacturing self-sealing tires and which iscomprised of (a) the reaction product of polyisobutylene and a silane;and (b) a reinforcing filler. The sealant compositions also contain aperoxide to facilitate partial degradation of the polyisobutylene rubberduring the curing of the tire.

The subject invention further reveals an uncured pneumatic tire which iscomprised of a generally toroidal-shaped carcass with an outercircumferential tread, two spaced beads, at least one ply extending frombead to bead, sidewalls extending radially from and connecting saidtread to said beads, a sealant layer which is disposed inwardly from thesupporting carcass, and an innerliner which is disposed inwardly fromthe sealant layer, wherein said circumferential tread is adapted to beground-contacting, and wherein the sealant layer is comprised of (a) thereaction product of polyisobutylene and a silane, and (b) a reinforcingfiller. This sealant layer will also include a peroxide. In oneembodiment of this invention the peroxide will have an active oxygencontent of at least 6% and which is preferably greater than 7%.

The present invention also discloses a method of manufacturing apneumatic rubber tire having a puncture sealing feature which comprises:(1) building an unvulcanized tire comprised of a circumferential rubbertread, a supporting carcass therefor, two spaced beads, two rubbersidewalls connecting said beads, an inner liner and a solid sealantformulation layer disposed inwardly from said supporting carcass andoutwardly from said inner liner wherein said solid sealant formulationlayer is comprised of (a) the reaction product of polyisobutylene and asilane, (b) a peroxide, and (c) a reinforcing filler; and (2) shapingand vulcanizing said tire in a tire mold under conditions of heat andpressure and simultaneously forming in situ a puncture sealant layer insaid tire by both crosslinking and partially depolymerizing saidpolyisobutylene rubber in said sealant layer formulation.

The subject invention further reveals a cured pneumatic tire which iscomprised of a generally toroidal-shaped carcass with an outercircumferential tread, two spaced beads, at least one ply extending frombead to bead, sidewalls extending radially from and connecting saidtread to said beads, a sealant layer which is disposed inwardly from thesupporting carcass, and an innerliner which is disposed inwardly fromthe sealant layer, wherein said circumferential tread is adapted to beground-contacting, and wherein the sealant layer is comprised of (a) thereaction product of polyisobutylene and a silane, and (b) a reinforcingfiller.

The present invention further discloses a method for reacting a silanewith polyisobutylene to make a reaction product polyisobutylene and asilane comprising reacting the polyisobutylene and the silane in thepresence of a peroxide at an elevated temperature which is sufficient tocause the peroxide to break down thereby creating free radicals. Somerepresentative examples of silanes that can be used includebis[3-(triethoxysilyl)propyl] tetrasulfide,bis[3-(triethoxysilyl)propyl] disulfide, triethoxy octyl silane,triethoxy propyl silane, mercapto tri ethoxy silane, mercapto trimethoxy silane, and triethoxymethylsilane.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further illustrated by the accompanyingdrawings. These drawings represent two preferred embodiments of thepresent invention.

FIG. 1 is a cross-sectional view of a tire of this invention wherein thesealant layer is sandwiched between the innerliner and carcass of thetire.

FIG. 2 is a cross-sectional view of a pneumatic rubber tire of thisinvention wherein the self-sealant layer of the tire is located betweentwo layers of innerliner in the tire.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of this invention a solid sealant layer formulationincluding the reaction product of polyisobutylene rubber and a silanehaving no unsaturation is assembled into an unvulcanized rubber tireusing conventional tire building techniques. The solid sealant layerformulation is relatively easy to build into the tire because it is inthe form of a solid which is not excessively sticky or tacky. Thephysical nature of the solid sealant layer formulation is such that itsviscosity is high enough to permit easy handling during the construction(building) of the unvulcanized tire and during the vulcanization(curing) operation. In other words, the solid sealant layer formulationhas enough uncured strength (modulus) to retain its shape duringbuilding, enough tack to stick to adjacent layers during building andenough strength to retain its shape during the application of the highpressure during vulcanization. However, it also is not too tacky anddoes not stick to undesired materials, such as the building drum.

The solid sealant layer formulation is assembled into the uncured tireinwardly from the tire supporting carcass of the tire. In most cases itwill be built into the tire between the supporting carcass and theinnerliner of the tire as is illustrated in FIG. 1 . The innerliner isan air barrier layer that serves to keep air or another gas, such asnitrogen, which is used to inflate the tire for escaping through thetire structure by diffusion. The innerliner is typically comprised of ahalobutyl rubber or some other suitable material having a high degree ofresistance to gas permeation. In another embodiment of this inventionthe solid sealant layer formulation is built into the tire between twolayers of innerliner as is illustrated in FIG. 2 . In other words, it issandwiched between two or more layers of innerliner or between one ormore innerliner layers and the tire carcass.

After an unvulcanized tire is built so as to include a layer of thesolid sealant formulation it is vulcanized utilizing conventionaltechniques. After the unvulcanized pneumatic rubber tires of thisinvention are assembled they are vulcanized using a normal tire curecycle. In the practice of this invention the unvulcanized tires can becured over a wide temperature range, such as a temperature which iswithin the range of about 100° C. to about 200° C. However, it isgenerally preferred for the tires of this invention to be cured at atemperature ranging from about 130° C. to about 170° C. It is typicallymore preferred for the tires of this invention to reach a maximumtemperature ranging from a 140° C. to 165° C. during vulcanization. Forinstance, it is typically optimal for the tire to reach a maximum curingtemperature which is within the range of 160° C. to 165° C. It isgenerally preferable for the cure cycle used to vulcanize the uncuredtires to have a duration which is within the range of about 8 minutes toabout 60 minutes. In the practice of this invention the uncured tireswith normally be cured for a period which is within the range of about10 minutes to 25 minutes with the cure period preferably being fromabout 10 minutes to 17 minutes, and most preferably being within therange of about 11 minutes to 13 minutes. Any standard vulcanizationprocess can be used such as heating in a press or mold and/or heatingwith superheated steam or hot air. In any case, the uncured tire can bebuilt, shaped, molded and cured by various methods which are known andwhich are readily apparent to those having ordinary skill in the art.

During the vulcanization of the tire the reaction product of thepolyisobutylene and the silane as well as other rubber components in thesolid sealant formulation will partially depolymerize at the elevatedvulcanization temperature to produce a highly effective puncture-sealantcomposition. Thus, the solid sealant layer formulation is transformed insitu into a puncture sealant layer during the curing of the tire. Thispuncture-sealant composition has a relatively low viscosity which allowsit to flow into punctures so as to seal them thereby stopping orhindering the escape of the gas used to inflate the tire.

The rubber component of the sealant layer can be comprised entirely ofthe reaction product of the polyisobutylene rubber and the silane or itcan include other desired rubbery polymers such as butyl rubber,halogenated butyl rubbers, or polyisobutylene rubber (which has not beenreacted with a silane). The rubbery component of the sealant layer willtypically contain at least about 10 phr (parts by weight per 100 partsof rubber) of the reaction product of the polyisobutylene rubber and thesilane. The rubbery component of the sealant layer will more typicallycontain at least 20 phr, 40 phr, 60 phr, or 80 phr of the reactionproduct of the polyisobutylene rubber and the silane with the balancerubbery component being other rubbery polymers. The reaction product ofthe polyisobutylene and the silane will be present in the sealantcomposition at a level which is within the range of 5 phr to 20 phr, ata level which is within the range of 20 phr to 40 phr, at a level whichis within the range of 40 phr to 60 phr, at a level which is within therange of 60 phr to 80 phr, or at a level which is within the range of 80phr to 100 phr. The other rubbery polymers which are optionally usedinclude butyl rubbers, halobutyl rubbers, or polyisobutylene rubbers.

Tires made in accordance with this invention are depicted in FIG. 1 andFIG. 2 . In FIG. 1 a self-sealing pneumatic rubber tire 2 of thisinvention is shown wherein the tire has sidewalls 3, a supportingcarcass 4, inextensible beads 5, an innerliner (air barrier layer) 6, asealant layer 7, and an outer circumferential tread (tread portion) 8.The individual sidewalls 3 extend radially inward from the axial outeredges of the tread portion 8 to join the respective inextensible beads5. The supporting carcass 4 acts as a supporting structure for the treadportion 8 and sidewalls 3. The sealant layer 7 is disposed inwardly fromsaid supporting carcass 4 and outwardly from said innerliner 6. Theouter circumferential tread 8 is adapted to be ground contacting whenthe tire is in use. In this embodiment of the invention, the innerliner6 is disposed inwardly from said supporting carcass 4.

In FIG. 2 a self-sealant pneumatic rubber tire 10 of another embodimentof this invention is depicted. This pneumatic tire of the tubeless typeincludes a tread portion 11, a crown area 12, sidewalls 13, a supportingcarcass 14, inextensible beads 15, an innerliner 16, and sealant layer17. In this embodiment of the present invention the sealant layer 17 issandwiched between two layers of innerliner 16. This, sealant layer 17is disposed inwardly from one layer of innerliner and outwardly fromanother layer of innerliner. Both layers of innerliner 16 and thesealant layer 17 are disposed inwardly from the supporting carcass 14.

In one embodiment of this invention, the reaction product ofpolyisobutylene and the silane is substituted for all or part ofpolyisobytylene used in the sealant formulations described in U.S.patent application Ser. No. 17/468,049, filed on Sep. 7, 2021. Theteachings of U.S. patent application Ser. No. 17/468,049 areincorporated by reference herein in their entirety. In any case, thereaction product of polyisobutylene and the silane can be substitutedfor 10 percent to 25 percent, 25 percent to 50 percent, 50 percent to 75percent, or 75 percent to 100 percent of the polyisobutylene called forin the solid sealant layer formulations described in U.S. patentapplication Ser. No. 17/468,049. These solid sealant layer formulationsare comprised of (a) polyisobutylene, (b) a peroxide, and (c) areinforcing filler, wherein the polyisobutylene is present in thesealant layer at a level of at least 50 weight percent, based upon thetotal weight of elastomers in the sealant formulation. Thepolyisobutylene can represent at least 75 weight percent, at least 90weight percent, at least 94 weight percent, at least 96 weight percent,at least 98 weight percent, or at least 99 weight percent, of the totalweight of elastomers in the sealant formulation. In fact, the sealantlayer formulation can be void of other elastomers. The solid sealantlayer formulation will contain less than 50 weight percent butyl rubber,will typically contain less than 40 weight percent butyl rubber, willnormally contain less than 20 weight percent butyl rubber, willpreferably contain less than 10 percent butyl rubber, will morepreferably contain less than 5 percent butyl rubber, and will mostpreferably contain less than 1 weight percent butyl rubber. The solidsealant layer formulation will typically be void of butyl rubber,halogenated butyl rubbers, natural rubber, synthetic polyisoprenerubber, emulsion styrene-butadiene rubber, solution styrene-butadienerubber, isoprene-butadiene rubber, styrene-isoprene-butadiene rubber,styrene/butadiene diblock polymers, styrene/butadiene/styrene triblockpolymers, neoprene, nitrile rubber, ethylene-propylene rubbers, andethylene-propylene-diene monomer rubbers.

The polyisobutylene rubber (PIB) utilized in this embodiment of thisinvention is a high molecular weight homopolymer of isobutylene. It willtypically have a weight average molecular weight which is within therange of 100,000 to 800,000, it will more typically have a weightaverage molecular weight which is within the range of 250,000 to600,000, it will preferably have a weight average molecular weight whichis with the range of 300,000 to 550,000, and it will more preferablyhave a weight average molecular weight which is within the range of300,000 to 450,000. The polyisobutylene rubber will normally have apolydispersity (Mw/Mn) which is within the range of 2.0 to 2.8, and aglass transition temperature which is within the range of −60° C. to−68° C. The polyisobutylene rubber will also typically have a viscosityaverage molecular weight which is within the range of 300,000 to600,000, a polydispersity (Mw/Mn) which is within the range of 2.1 to2.7, and a glass transition temperature which is within the range of−61° C. to −67° C.

The polyisobutylene rubber will preferably have a viscosity averagemolecular weight which is within the range of 350,000 to 550,000, apolydispersity (Mw/Mn) which is within the range of 2.2 to 2.6, and aglass transition temperature which is within the range of −62° C. to−66° C. The polyisobutylene rubber will more preferably have a viscosityaverage molecular weight which is within the range of 400,000 to450,000, a polydispersity (Mw/Mn) which is within the range of 2.3 to2.5, and a glass transition temperature which is within the range of−63° C. to −65° C. The polyisobutylene rubber will most preferably havea viscosity average molecular weight which is within the range of375,000 to 500,000, a polydispersity (Mw/Mn) of about 2.4, and a glasstransition temperature of about −64° C. The polyisobutylene rubber canoptionally be stabilized with a small amount of an antioxidant, such asfrom about 100 ppm to 1,000 ppm of an antioxidant. Such antioxidantswill typically be incorporated into the polyisobutylene rubber at alevel of about 300 ppm to about 700 ppm. A wide variety of antioxidantscan be employed with butylated hydroxytoluene (BHT) typically beingused.

The peroxide compounds utilized in the practice of this invention arethose generally used for the crosslinkage of rubbery polymers.Preferably peroxide compounds which disintegrate only at hightemperatures, above about 100° C. are utilized. Some representativeexamples of such peroxides include tert-butyl perbenzoate and dialkylperoxides with the same or different radicals, such as dialkylbenzeneperoxides and alkyl peresters. Preferably the peroxide vulcanizing agentemployed will contain two peroxide groups. Frequently the peroxidegroups are attached to a tertiary-butyl group. The basic moiety on whichthe two peroxide groups are suspended can be aliphatic, cycloaliphatic,or aromatic radicals. Some representative examples of such peroxideinclude: bis(α,α-dimethylbenzyl) peroxide (more commonly known asdicumyl peroxide); 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane;1,1-di-t-butyl peroxy-3,3,5-trimethyl cyclohexane;2,5-dimethyl-2,5-di(t-butyl peroxy) hexyne-3; p-chlorobenzyl peroxide;2,4-dichlorobenzyl peroxide; 2,2-bis-(t-butyl peroxy)-butane; di-t-butylperoxide; benzyl peroxide; 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane;and 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane. Such peroxidevulcanizing agents can be added to the polymer composition layer in pureform (100 percent active peroxide), but are typically employed on aninert, free-flowing mineral carrier or an oil, such as silicon oil.Calcium carbonate is an inert mineral carrier which is frequentlyutilized for this purpose. Such peroxide carrier compositions normallycontaining from about 30 weight percent to 55 weight percent activeperoxide and typically contain from 35 weight percent to 50 weightpercent active peroxide. For instance, the peroxide carrier compositioncan contain from about 38 weight percent to about 43 weight percentactive peroxide, such as dicumyl peroxide, on a mineral carrier, such ascalcium carbonate. The peroxide will normally be included in the solidsealant layer formulation used in the practice of this invention at alevel which is within the range of 2 phr to 7 phr (based upon activeperoxide) and will typically be present at a level which is within therange of 2.5 phr to 5 phr. It is preferred for the peroxide to bepresent at a level which is within the range of 3 phr to 4.2 phr and ismore preferably included at a level which is within the range of 3.5 phrto 4 phr. The term “phr” stands for parts by weight per 100 parts byweight of rubber.

In the practice of this invention it is preferred to utilize a peroxidethat has an active oxygen content (AOC) of at least 2. Active oxygencontent is determined by dividing the weight of active oxygen atoms inthe compound by its total molecular weight (this is done on the basis ofone active oxygen atom for each peroxide moiety (—O—O—) in the compound.For example, t-butyl cumyl peroxide has one active oxygen atom(molecular weight of 16) and a total molecular weight of 208.Accordingly, the active oxygen content of t-butyl cumyl peroxide is16/208 which is 0.077 or 7.7%. In any case, peroxides having activeoxygen contents of greater than 7%, 8%, 9%, or even 10% are highlypreferred. This is because they generate less gas during the tire curingprocess than do peroxides having lower active oxygen contents. For thisreason, benzoyl peroxide (AOC of 6.5), t-butyl cumyl peroxide (AOC of7.7), and di-t-butyl peroxide (AOC of 11.0%) are preferred for use inthe practice of this invention. It should also be noted that theseperoxides can also be utilized beneficially in conventional butyl rubberbased sealant formulations that include typically compoundingingredients as described herein.

A reinforcing filler is included in the solid sealant layer formulationto give it a consistency which facilitates building it into uncuredtires. A wide variety of reinforcing fillers can be used for thispurpose. For example, the filler can be carbon black, graphite,graphene, carbon nanotubes, wollastonite, silica, crystalline silica,clay, 2:1 layered silicate clays, talc, diatomaceous earth, calciumcarbonate (CaCO₃), calcium silicate, starch, lignin, alumina, orpolypropylene. The 2:1 layered silicate clays that are typicallypreferred include montmorillonite, bentonite, hectorite, saponite,nontronite, beidellite, fluorohectorite, stevensite, volkonskoite,sauconite laponite, related analogs thereof and their physical blends.Clays that have been chemically modified to make them compatible withorganic materials are preferred and are generally referred to as“organophilic” clays or “organo-clays”. The basic starting material usedto make organophilic clay is an exchangeable clay of the smectite groupand can include montmorillonite (commonly known and mined as bentonite),hectorite, saponite, attapulgite and sepolite. These clays includeexchangeable cationic species such as sodium, potassium or calcium ionson their surface and between clay galleries or layers. In the course ofmanufacturing an organophilic clay, at least a portion of theseexchangeable cationic species are substituted by an organic cation suchas a quaternary amine, an organophosphorus ion, any other ion of thetype known in the art as an onium ion, or the like.

The graphene that can be used in the solid sealant layer formulations ofthis invention is a one-atom-thick crystalline form of carbon in whichcarbon atoms are held together by sigma bonds that are arranged in atwo-dimensional honeycomb lattice. More specifically graphene is acrystalline allotrope of carbon with 2-dimensional properties. Thecarbon atoms in graphene are densely packed in a regular atomic-scalehexagonal (chicken wire) pattern. Each atom has four bonds, one σ bondwith each of its three neighbors and one H-bond that is oriented out ofplane. The distance between adjacent carbon atoms in graphene isapproximately 0.142 nanometers. The graphene that can be advantageouslyused as a reinforcing filler in the practice of this invention can havezig-zag, armchair, K-region, gulf, bay, cove, and fjord edge topologies.Typically, at least 50 percent, 60 percent, 70 percent, or 80 percent ofthe carbon-carbon bonds on the edges of the graphene structure will bein the zig-zag configuration, the armchair configuration, or the bayconfiguration. In many cases, at least 40 percent, 50 percent, or 60percent of the carbon-carbon bonds on the edges of the graphenestructure will be in the zig-zag configuration. In one embodiment atleast 40 percent, 50 percent, or 60 percent of the carbon-carbon bondson the edges of the graphene structure will be in the armchairconfiguration. In another embodiment at least 40 percent, 50 percent, or60 percent of the carbon-carbon bonds on the edges of the graphenestructure will be in the bay configuration. Typically, less than 40percent of the carbon-carbon bonds on the edges of the graphenestructure will be in the cove configuration and more typically less than30 percent of the carbon-carbon bonds on the edges of the graphenestructure will be in the cove configuration. In another embodiment lessthan 40 percent of the carbon-carbon bonds on the edges of the graphenestructure will be in the cove configuration and less than 30 percent ormore typically less than 20 percent of the carbon-carbon bonds on theedges of the graphene structure will be in the fjord configuration.

The graphene that can optionally be used as a reinforcing filler in thepractice of this invention is exfoliated into nano-scaled graphene plate(NGP) material that is essentially comprised of individual single sheetsof graphene or a plurality of sheets of graphite planes. Each graphiteplane, also referred to as a graphene plane or basal plane and iscomprised of a two-dimensional hexagonal structure of carbon atoms. Eachplane has a length and a width parallel to the graphite plane and athickness orthogonal to the graphite plane characterized in that atleast one of the values of length, width, and thickness is 100nanometers (nm) or smaller. Preferably, all length, width and thicknessvalues are smaller than 100 nm. This NGP material can be produced by aprocess the method described in U.S. Pat. No. 7,071,258 which comprisingthe steps of: (a) carbonization or graphitization to produce a polymericcarbon, (b) exfoliation or expansion of graphite crystallites in thepolymeric carbon to delaminate or separate graphene planes, and (c)mechanical attrition of the exfoliated structure to nanometer-scaledplates. The teachings of U.S. Pat. No. 7,071,258 are incorporated hereinby references for the purpose or describing graphene that can beutilized in the practice of this invention and methods for manufacturingsuch graphene. In the practice of this invention it is preferred for thegraphene to be comprised of individual single sheets of graphene (singlegraphene planes or single basal planes).

The reinforcing filler is typically included at a level which is withinthe range of about 10 phr to about 75 phr and is more typically includedat a level which is within the range of 20 phr to 50 phr. Thereinforcing filler is normally included at a level which is within therange of about 25 phr to about 45 phr, is preferably included at a levelwhich is within the range of 30 phr to 40 phr, and is more preferablyincluded at a level which is within the range of 32 phr to 38 phr. Incases where polypropylene is utilized as a filler lower levels arerequired since it has been found to be highly effective. Morespecifically, in cases where polypropylene is used as a filler about 35percent to 40 percent less material is required than is the case withconventional fillers, such as carbon black and mineral fillers. The useof polypropylene as a filler also offers an additional advantage in thatit breaks down during the curing of the tire to work in conjunction withthe polyisobutylene rubber as a sealant. In other words, polypropyleneoffers a unique advantage in that it acts both as a filler in buildingthe tire and subsequently as a sealant in the cured tire. Low molecularweight polypropylene is preferred for use as a filler in the practice ofthis invention. Such low molecular weight polypropylene typically has aweight average molecular weight (M_(w)) which is within the range ofabout 4,000 to about 40,000. The low molecular weight polypropylene willnormally have a weight average molecular weight which is within therange of 6,000 to 25,000, will preferably have a weight averagemolecular weight which is within the range of 8,000 to 20,000, and willmost preferably have a weight average molecular weight which is withinthe range of 10,000 to 15,000. It should also be noted thatpolypropylene can also be beneficially utilized in conventional butylrubber based sealant formulations that include typically compoundingingredients as described herein.

The solid sealant layer formulation used in the practice of thisinvention can optionally include one or more processing oils. A widevariety of processing oils can be used. Suitable processing oils mayinclude various oils as are known in the art, including aromatic,paraffinic, naphthenic, triglyceride oils, and low PCA oils, such asMES, TDAE, SRAE and heavy naphthenic oils. Suitable low PCA oils mayinclude those having a polycyclic aromatic content of less than 3percent by weight as determined by the IP346 method. Procedures for theIP346 method may be found in Standard Methods for Analysis & Testing ofPetroleum and Related Products and British Standard 2000 Parts, 2003,62nd edition, published by the Institute of Petroleum, United Kingdom,the teachings of which are incorporated herein by reference. Thetriglyceride oils that can be used include vegetable oils, including butnot limited to vegetable oils, soybean oil, canola oil (Rapeseed oil),corn oil, cottonseed oil, olive oil, palm oil, safflower oil, sunfloweroil, coconut oil, and peanut oil. Castor oil, soybean oil, and corn oilare preferred oils for use in the solid sealant layer formulations ofthis invention. Castor oil is a triglyceride oil that containsapproximately 87 percent ricinoleic acid, 7 percent oleic acid, 3percent linoleic acid, 2 percent palmitic acid, and 1 percent stearicacid. The processing oil will typically be employed at a level which iswithin the range of about 1 phr to about 20 phr and will more typicallybe employed at a level which is within the range of 1 phr to 10 phr. Inmost cases the processing oil will be included at a level which iswithin the range of about 2 phr to about 5 phr and will preferably beemployed at a level which is within the range of 2 phr to 4 phr.

Various pigments or colorants can also optionally be included in thesealant formulations of this invention. By including one or morepigments or colorants in the sealant formulation the fact that the tirehas in fact been punctured and the location of puncture can more readilybe identified. A wide variety of colors can be used for this purposewith lights colors which stand out from the characteristic black colorof tire treads being preferred. For example, white, red, orange, yellow,green, or blue pigments or colorants can optionally be included.Titanium dioxide can be utilized to impart a brilliant white color, rediron pigment can be used to impart a brilliant red color, or pigmentyellow 12 can be used to impart a brilliant yellow color. The pigment orcolorant will typically be utilized in a quantity that will makepunctures in the tire more readily apparent and will normally be used ata level which is within the range about 1 phr to about 5 phr, and willpreferably be used at a level which is within the range of 2 phr to 4phr.

Both organic and inorganic pigments can be utilized. In most cases thepigment or colorant will be of a white, red, orange, yellow, green, orblue color. Some representative examples of pigments that can beutilized include, but are not limited to, Pigment Yellow 1 (CAS No.2512-29-0), Pigment Yellow 110 (CAS No. 5590-18-1), Pigment Yellow 12(CAS No. 15541-56-7), Pigment Yellow 126 (CAS No. 90268-23-8), PigmentYellow 127 (CAS No. 68610-86-6), Pigment Yellow 13 (CAS No. 5102-83-0),Pigment Yellow 138 (CAS No. 30125-47-4), Pigment Yellow 14 (CAS No.5468-75-7), Pigment Yellow 150 (CAS No. 68511-62-6), Pigment Yellow 151(CAS No. 31837-42-0), Pigment Yellow 154 (CAS No. 68134-22-5), PigmentYellow 168 (CAS No. 71832-85-4), Pigment Yellow 17 (CAS No. 4531-49-1),Pigment Yellow 174 (CAS No. 78952-72-4), Pigment Yellow 180 (CAS No.77804-81-0), Pigment Yellow 183 (CAS No. 65212-77-3), Pigment Yellow 191(CAS No. 129423-54-7), Pigment Yellow 3 (CAS No. 6486-23-3), PigmentYellow 34 (CAS No. 1344-37-2), Pigment Yellow 42 (CAS No. 51274-00-1),Pigment Yellow 65 (CAS No. 6528-34-3), Pigment Yellow 74 (CAS No.6358-31-2), Pigment Yellow 75 (CAS No. 52320-66-8), Pigment Yellow 81(CAS No. 22094-93-5), Pigment Yellow 83 (CAS No. 5567-15-7), C.I.Pigment Yellow 42 (iron oxide), C.I. Pigment Yellow 34 (lead chromates),C.I. Pigment Yellow 184 (bismuth vanadates), C.I. Pigment Yellow 53(nickel antimony), C.I. Pigment Orange 20 (cadmium sulfide), C.I.Pigment Red 101 (iron oxide), C.I. Pigment Red 104, C.I. Pigment Red 29(ultramarine pigment), C.I. Pigment Blue 29 (ultramarine pigment), C.I.Pigment Blue 28, C.I. Pigment Blue 36, C.I. Pigment Violet 15(ultramarine pigment), C.I. Pigment Violet 16 (manganese violet),Pigment Green 17 (chrome oxide green), C.I. Pigment Green 19(cobalt-based mixed metal oxides), C.I. Pigment Green 26 (cobalt-basedmixed metal oxides), and C.I. Pigment Green 50 (cobalt-based mixed metaloxides).

Some additional inorganic pigments that can be used include Ultramarineblue, Persian blue, Cobalt blue (CAS No. 1345-16-0), Curlean blue,Egyptian blue, Han blue (BaCuSi₄O₁₀), Azurite blue (Cu₃(CO₃)₂(OH)₂,Prussian blue (CAS No. 14038-43-8), YInMn blue (Oregon blue), Realgarred (α-As₄S₄), cadmium red (Cd₂SSe), Cerium sulfide red, Venetian red(Fe₂O₃), Red Ochre (anhydrous Fe₂O₃), Burnt sienna red, Red lead(Pb₃O₄), Vermilian red, Cinnabar red, Ultramarine violet, Han purple(BaCuSi₂O₆), Cobalt violet (CO₃(PO₄)₂), Manganese violet (NH₄MnP₂O₇),Purple of Cassius, Primrose yellow (BiVO₄), Cadmium yellow (CdS), Chromeyellow (PbCrO₄), Aureolin yellow (K₃Co(NO₂)₆), Yellow Ochre (Fe₂O₃·H₂O),Naples yellow, Titanium yellow (NiO·Sb₂O₃·20TiO₂), Zinc yellow (ZnCrO₄),and Chrome orange (PbCrO₄·PbO).

Polyethylene glycol can also optionally be included in the sealantformulations of this invention. The polyethylene glycol will typicallyhave a molecular weight which is within the range of 100 to 12, 000 andwill more typically have a molecular weight which is within the range of4,000 to 8,000. In cases where polyethylene glycol is utilized it willtypically be included at a level which is within the range of about 0.1phr to about 2 phr, preferably within the range of 0.2 phr to 1 phr, andmost preferably within the range of 0.3 phr to 0.7 phr.

The various components of the solid sealant layer formulation can bemixed together using any convenient rubber mixing equipment, such as aBanbury mixer or a mill mixer. In any case, this rubber compositionshould have sufficient viscosity and unvulcanized adhesion (greenstrength) to enable its incorporation into an unvulcanized tire withoutdeparting from standard, long standing tire building techniques andwithout the use of complicated auxiliary tire building equipment. In themethod of this invention, the polymer composition can be formed into astrip of unvulcanized rubber that is assembled into the tire.

The strip of puncture sealant formulation employed should extend fromone shoulder of the tire to the other, in other words, it should coverthe crown area of the tire. The thickness of the sealant layer can varygreatly in an unvulcanized puncture sealant tire. Generally, thethickness of the polymer composition layer will range from about 0.2 mmto about 8.5 mm. It is generally preferred for the sealant compositionlayer to have a thickness of 3 mm to 6 mm and is typically mostpreferred for the sealant layer to have a thickness which is within therange of 4 mm to 5 mm. In passenger tires it is normally most preferredfor the polymer composition layer to have a thickness of about 4.5 mm.

In one scenario tires can be built in accordance with this invention byfirst applying an innerliner to a building drum with the strip of thesealant formulation of this invention subsequently being applied to thelayer of innerliner. After the strip of sealant formulation is assembledinto the unvulcanized tire other normal tire components can then beassembled into the tire using standard, known procedures. In thisscenario the sealant layer will be sandwiched between the innerliner andthe tire carcass. In another embodiment of this invention a second layerof innerliner can be applied on top of the sealant formulation with thecarcass subsequently being applied on top of the second sealant layer.In this embodiment the sealant formulation will be sandwiched betweenthe two layers of innerliner. In other words, the sealant compositioncan be built into the tire so as to be sandwiched between two layers ofinnerliner or between a layer of innerliner and the carcass of the tire.

In another embodiment of this invention a sealant composition having amuch lower viscosity (an essentially liquid formulation) can be builtinto the tire as a sealant layer which is embedded in a stiff material.Such a technique and such sealant formulations are described in U.S.Provisional Patent Application Ser. No. 63/252,700, filed on Oct. 16,2021. The teachings of U.S. Provisional Patent Application Ser. No.63/252,700 are incorporated by reference herein. In any case, thereaction product of polyisobutylene and a silane can be included in thelow viscosity sealant formulations described in U.S. Provisional PatentApplication Ser. No. 63/252,700 to reduce hysteresis and to accordinglyimprove the fuel economy of tire make therewith. The level of thereaction product of polyisobutylene and a silane incorporated into thesealant formulation can vary widely depending upon the ultimate sealantcharacteristics desired. For instance, such sealant formulations cancontain from 10 phr to 25 phr, 25 phr to 50 phr, 50 phr to 75 phr, or 75phr to 100 phr of the reaction product of polyisobutylene and thesilane. In cases where high levels of the reaction product of thepolyisobutylene and the silane are included in such formulations thepolyisobutylene used in making the reaction product will typically be ofa relatively low molecular weight.

As is explained in U.S. Provisional Patent Application Ser. No.63/252,700, such polyisobutylene of a relatively low molecular weightwill typically have a weight average molecular weight which is withinthe range of 40,000 to 120,000, and it will more typically have a weightaverage molecular weight which is within the range of 50,000 to 110,000.For instance the polyisobutylene can have a weight average molecularweight which is within the range of 40,000 to 60,000, which is withinthe range of 60,000 to 80,000, or which is within the range of 80,000 to120,000. The polyisobutylene will typically have a viscosity averagemolecular weight which is within the range of 30,000 to 50,000, which iswithin the range of 50,000 to 70,000, or which is within the range70,000 to 95,000. The polyisobutylene will also typically have a numberaverage molecular weight which is within the range of 20,000 to 30,000,which is within the range of 30,000 to 50,000, or which is within therange of 50,000 to 70,000. Additionally, the polyisobutylene willnormally have a polydispersity (Mw/Mn) which is within the range of 1.6to 3.4, and a glass transition temperature which is within the range of−55° C. to −70° C. The polyisobutylene will normally have a glasstransition temperature which is within the range of −62° C. to −66° C.and which is more typically within the range of −63° C. to −65° C.

In another embodiment of this invention tires can be manufactured byextruding such a low viscosity sealant formulation including thereaction product of the polyisobutylene and the silane into the tire asits sealant layer. Such techniques for manufacturing tires are describedby the teachings of U.S. Provisional Patent Application No. 63/214,515,filed on Jun. 24, 2021. The teachings of U.S. Provisional PatentApplication No. 63/214,515 are incorporated by reference herein.

In still another embodiment of this invention a foam can be included inthe sealant layer containing the reaction product of the polyisobutyleneand the silane for the purpose of noise suppression. Self-sealing tireswhich include foam for noise reduction are described in U.S. ProvisionalPatent Application No. 63/252,677, filed on Oct. 6, 2021. The teachingsof U.S. Provisional Patent Application No. 63/252,677 are incorporatedherein by reference.

The following examples are included to further illustrate the method ofmanufacturing the self-sealing pneumatic rubber tires of this invention.These examples are intended to be representative of the presentinvention and are not to be regarded as limiting the scope of theinvention or the manner in which it can be practiced. Unlessspecifically indicated otherwise, parts and percentages are given byweight.

Examples 1-3

In these experiments the effect of a sulfur containing silane on apolyisobutylene elastomer was probed. It is known that polyisobutylenedecomposes at high temperatures especially when introduced to radicalsdue to peroxide decomposition. In these experiments the formulationsspecified in Table 1 were evaluated and relevant compound properties aregiven in Table 2.

TABLE 1 Formulations of Evaluated Samples PIN + Neat PIB + PIB + Si266 +PIB Peroxide Si266 Peroxide N50* 100 100 100 100 Si266 1 1 DiCup40C 6 6*Oppanol ® N50 polyisobutylene rubber (PIB) with M_(v) = 425,000; M_(w)= 565,000; M_(w)/M_(n) = 2.4; Tg = −64° C.; and Staudinger Index Jo =128-150 cm3/g in isooctane @ 20° C.

TABLE 2 Properties of the Evaluated Samples PIB + Neat PIB + PIB +Si266 + PIB Peroxide Si266 Peroxide Results at a temperature of 40° C.G′ @ 5.0% 0.305 MPa 0.009 MPa 0.293 MPa 0.052 MPa Tan δ @ 5.0% 0.14 2.130.12 0.90 Results at a temperature of 60° C. G′ @ 5.0% 0.267 MPa 0.002MPa  0.263  0.020 Tan δ @ 5.0% 0.18 4.21 0.16 1.37

From the results in Table 2, it can be seen that the silane did notchange the properties of the polyisobutylene significantly on its own(without the presence of a peroxide). The addition of the peroxide tothe polymer did indeed decrease the viscosity of the neatpolyisobutylene in accordance with this invention. However, the sampleswith the silane showed a significantly lesser decrease in viscosity.This indicates that some type of reaction between the silane and thepolyisobutylene took place. This can be further taken advantage of informulations that contain silica. More specifically, the silane canfirst be reacted with the silica (pretreated) and then through thisprocess reacted with the polyisobutylene to create a polyisobutylenetreated silica.

Variations in the present invention are possible in light of thedescription of it provided herein. The illustrations and correspondingdescriptions are not intended to restrict or limit the scope of theappended claims in any way. While certain representative embodiments anddetails have been shown for the purpose of illustrating the subjectinvention, it will be apparent to those skilled in this art that variouschanges and modifications can be made therein without departing from thescope of the subject invention. It is, therefore, to be understood thatchanges can be made in the particular embodiments described which willbe within the full intended scope of the invention as defined by thefollowing appended claims.

What is claimed is:
 1. A sealant composition which is particularlyuseful in manufacturing self-sealing tires and which is comprised of (a)the reaction product of polyisobutylene and a silane having nounsaturation; and (b) a reinforcing filler.
 2. The sealant compositionof claim 1 wherein said composition is further comprised of a peroxide.3. The sealant composition as specified in claim 1 wherein peroxide ispresent at a level which is within the range of 0.5 phr to 14 phr. 4.The sealant composition as specified in claim 1 wherein peroxide ispresent at a level which is within the range of 3.5 phr to 5 phr.
 5. Thesealant composition as specified in claim 1 wherein the peroxide has anactive oxygen content of at least 2%.
 6. The sealant composition asspecified in claim 1 wherein the peroxide has an active oxygen contentof at least 10%.
 7. The sealant composition as specified in claim 1wherein the reinforcing filler includes polypropylene, and wherein thepolypropylene is low molecular weight polypropylene having a weightaverage molecular weight which is within the range of about 4,000 toabout 40,000.
 8. The sealant composition as specified in claim 7 whereinsaid sealant composition is void of reinforcing fillers other than thepolypropylene and carriers for the peroxide.
 9. The sealant compositionof claim 1 where the silane is selected from the group consisting ofBis[3-(triethoxysilyl)propyl] tetrasulfide,Bis[3-(triethoxysilyl)propyl] disulfide, triethoxy octyl silane,triethoxy propyl silane, mercapto tri ethoxy silane, mercapto trimethoxy silane, and triethoxymethylsilane.
 10. The sealant compositionas specified in claim 1 wherein said sealant composition is void ofreinforcing fillers other than polypropylene.
 11. The sealantcomposition as specified in claim 1 wherein said sealant composition isfurther comprised of a red, orange, yellow, green, or blue pigment orcolorant, and wherein said sealant composition is void of carbon black.12. The sealant composition as specified in claim 1 wherein said sealantcomposition is void of natural rubber, synthetic polyisoprene rubber,emulsion styrene-butadiene rubber, solution styrene-butadiene rubber,isoprene-butadiene rubber, styrene-isoprene-butadiene rubber,styrene/butadiene diblock polymers, styrene/butadiene/styrene triblockpolymers, neoprene, nitrile rubber, ethylene-propylene rubbers, andethylene-propylene-diene monomer rubbers.
 13. The sealant composition ofclaim 1 where the silane has been at least partially reacted with asilicate.
 14. The sealant composition of claim 1 wherein polyisobutyleneis partially substituted by a butyl rubber with an unsaturation levelbelow 3%.
 15. The sealant composition of claim 1 wherein polyisobutyleneis fully substituted by a butyl rubber with an unsaturation level below3%.
 16. An uncured pneumatic tire which is comprised of a generallytoroidal-shaped carcass with an outer circumferential tread, two spacedbeads, at least one ply extending from bead to bead, sidewalls extendingradially from and connecting said tread to said beads, a sealant layerwhich is disposed inwardly from the supporting carcass, and aninnerliner which is disposed inwardly from the sealant layer, whereinsaid circumferential tread is adapted to be ground-contacting, andwherein the sealant layer is comprised of the sealant composition ofclaim
 1. 17. A method of manufacturing a pneumatic rubber tire having apuncture sealing feature which comprises: (1) building an unvulcanizedtire comprised of a circumferential rubber tread, a supporting carcasstherefor, two spaced beads, two rubber sidewalls connecting said beads,an inner liner and a sealant formulation layer disposed inwardly fromsaid supporting carcass and outwardly from said inner liner wherein saidsolid sealant formulation layer is a solid layer which is comprised thesealant composition of claim 1; and (2) shaping and vulcanizing saidtire in a tire mold under conditions of heat and pressure andsimultaneously forming in situ a puncture sealant layer in said tire byboth crosslinking and partially depolymerizing said polyisobutylenerubber in said sealant layer formulation.
 18. A cured pneumatic tirewhich is comprised of a generally toroidal-shaped carcass with an outercircumferential tread, two spaced beads, at least one ply extending frombead to bead, sidewalls extending radially from and connecting saidtread to said beads, a sealant layer which is disposed inwardly from thesupporting carcass, and an innerliner which is disposed inwardly fromthe sealant layer, wherein said circumferential tread is adapted to beground-contacting, and wherein the sealant layer is comprised of thesealant composition of claim
 1. 19. A method for reacting a silanehaving no unsaturation with polyisobutylene to make a reaction productpolyisobutylene and a silane comprising reacting the polyisobutylene andthe silane in the presence of a peroxide at an elevated temperaturewhich is sufficient to cause the peroxide to break down thereby creatingfree radicals.
 20. The reaction product as specified in claim 19 whereinthe silane has no unsaturation, and wherein the silane has been firstpre-reacted with a silicate filler.